Measure and expose DNS programming latency from Kubernetes plugin. (#3171)

For now metric is measure only for headless services. Informer has been slighlty
refactored, so the code can measure latency without storing extra fields on
Endpoint struct.

Signed-off-by: Janek Łukaszewicz <janluk@google.com>

Suggestions from code review

Co-Authored-By: Chris O'Haver <cohaver@infoblox.com>

plugin/kubernetes/object/endpoint.go

@@ -44,10 +44,10 @@ type EndpointPort struct {
 func EndpointsKey(name, namespace string) string { return name + "." + namespace }
 
 // ToEndpoints converts an api.Endpoints to a *Endpoints.
-func ToEndpoints(obj interface{}) interface{} {
+func ToEndpoints(obj interface{}) (*api.Endpoints, *Endpoints) {
 	end, ok := obj.(*api.Endpoints)
 	if !ok {
-		return nil
+		return nil, nil
 	}
 
 	e := &Endpoints{
@@ -93,9 +93,7 @@ func ToEndpoints(obj interface{}) interface{} {
 		}
 	}
 
-	*end = api.Endpoints{}
-
-	return e
+	return end, e
 }
 
 // CopyWithoutSubsets copies e, without the subsets.

plugin/kubernetes/object/informer.go

@@ -5,19 +5,25 @@ import (
 	"k8s.io/client-go/tools/cache"
 )
 
-// NewIndexerInformer is a copy of the cache.NewIndexInformer function, but allows Process to have a conversion function (ToFunc).
-func NewIndexerInformer(lw cache.ListerWatcher, objType runtime.Object, h cache.ResourceEventHandler, indexers cache.Indexers, convert ToFunc) (cache.Indexer, cache.Controller) {
+// NewIndexerInformer is a copy of the cache.NewIndexerInformer function, but allows custom process function
+func NewIndexerInformer(lw cache.ListerWatcher, objType runtime.Object, h cache.ResourceEventHandler, indexers cache.Indexers, builder ProcessorBuilder) (cache.Indexer, cache.Controller) {
 	clientState := cache.NewIndexer(cache.DeletionHandlingMetaNamespaceKeyFunc, indexers)
 
-	fifo := cache.NewDeltaFIFO(cache.MetaNamespaceKeyFunc, clientState)
-
 	cfg := &cache.Config{
-		Queue:            fifo,
+		Queue:            cache.NewDeltaFIFO(cache.MetaNamespaceKeyFunc, clientState),
 		ListerWatcher:    lw,
 		ObjectType:       objType,
 		FullResyncPeriod: defaultResyncPeriod,
 		RetryOnError:     false,
-		Process: func(obj interface{}) error {
+		Process:          builder(clientState, h),
+	}
+	return clientState, cache.New(cfg)
+}
+
+// DefaultProcessor is a copy of Process function from cache.NewIndexerInformer except it does a conversion.
+func DefaultProcessor(convert ToFunc) ProcessorBuilder {
+	return func(clientState cache.Indexer, h cache.ResourceEventHandler) cache.ProcessFunc {
+		return func(obj interface{}) error {
 			for _, d := range obj.(cache.Deltas) {
 
 				obj := convert(d.Object)
@@ -43,9 +49,8 @@ func NewIndexerInformer(lw cache.ListerWatcher, objType runtime.Object, h cache.
 				}
 			}
 			return nil
-		},
+		}
 	}
-	return clientState, cache.New(cfg)
 }
 
 const defaultResyncPeriod = 0

plugin/kubernetes/object/object.go

@@ -16,14 +16,18 @@
 package object
 
 import (
-	"k8s.io/apimachinery/pkg/apis/meta/v1"
+	v1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/runtime/schema"
 	"k8s.io/apimachinery/pkg/types"
+	"k8s.io/client-go/tools/cache"
 )
 
 // ToFunc converts one empty interface to another.
 type ToFunc func(interface{}) interface{}
 
+// ProcessorBuilder returns function to process cache events.
+type ProcessorBuilder func(cache.Indexer, cache.ResourceEventHandler) cache.ProcessFunc
+
 // Empty is an empty struct.
 type Empty struct{}
 

plugin/kubernetes/object/pod.go

@@ -16,8 +16,14 @@ type Pod struct {
 	*Empty
 }
 
-// ToPod converts an api.Pod to a *Pod.
-func ToPod(obj interface{}) interface{} {
+// ToPod returns a function that converts an api.Pod to a *Pod.
+func ToPod(skipCleanup bool) ToFunc {
+	return func(obj interface{}) interface{} {
+		return toPod(skipCleanup, obj)
+	}
+}
+
+func toPod(skipCleanup bool, obj interface{}) interface{} {
 	pod, ok := obj.(*api.Pod)
 	if !ok {
 		return nil
@@ -35,7 +41,9 @@ func ToPod(obj interface{}) interface{} {
 		return nil
 	}
 
-	*pod = api.Pod{}
+	if !skipCleanup {
+		*pod = api.Pod{}
+	}
 
 	return p
 }

plugin/kubernetes/object/service.go

@@ -26,8 +26,14 @@ type Service struct {
 // ServiceKey return a string using for the index.
 func ServiceKey(name, namespace string) string { return name + "." + namespace }
 
-// ToService converts an api.Service to a *Service.
-func ToService(obj interface{}) interface{} {
+// ToService returns a function that converts an api.Service to a *Service.
+func ToService(skipCleanup bool) ToFunc {
+	return func(obj interface{}) interface{} {
+		return toService(skipCleanup, obj)
+	}
+}
+
+func toService(skipCleanup bool, obj interface{}) interface{} {
 	svc, ok := obj.(*api.Service)
 	if !ok {
 		return nil
@@ -58,7 +64,9 @@ func ToService(obj interface{}) interface{} {
 		s.ExternalIPs[li+i] = lb.IP
 	}
 
-	*svc = api.Service{}
+	if !skipCleanup {
+		*svc = api.Service{}
+	}
 
 	return s
 }